The present invention relates to apparatus for sensing the motion of a rotating member and, depending on the momentary angular displacement, for sending a signal dependent on the rotated position of the part whose motion is sensed.
It is an object of the present invention to provide such apparatus, which will not require any significant alteration in the structure of the device whose rotating part is thus monitored.
It is known to provide such position-sensing devices for use, for example, in connection with rotary valves to send signals to a control center as to the closed, intermediate or open position of the valve and perhaps also to respond to signals received from the control center. This permits remote control of the valves. Such devices can embody limit switches to respond to the attainment of an end position by the valve rotor.
In a pipeline system, for example, there may be a number of valves whose opening and closing requires the intervention of an operator and so gives rise to the possibility of misadjustment. To avoid this, it is necessary to monitor the positions of the valves and to send signals to control equipment so as to initiate any required corrective action.
However, the sensors known heretofore require alteration of the internal construction of the device such as a valve, which is costly and requires special knowledge and skills. Moreover, such monitored devices are often authenticated and licensed mechanisms fitted with watertight and airtight and possibly explosion-proof packing, which must not be tampered with.